High polymer latices and methods and means for producing same

ABSTRACT

THE PREPARATION OF AQUEOUS LATICES FROM SOLVENT DISPERSIONS OF ELASTOMERS AND OTHER HIGH POLYMER COMPOSITIONS HAS PRESENTED PROBLEMS INCLUDING EXCESSIVE VISCOSITY DURING PROCESSING AND FOAMING AND COAGULATION, WHICH HAVE PRODUCED LOSSES AND INCREASED COSTS. HEREIN CONBINATIONS OF STEPS AND APPARATUS ARE DISCLOSED WHICH REDUCE OR ELIMINATE VARIOUS OF THESE PROBLEMS, ESPECIALLY COAGULUM; ENABLE THE PREPARATION OF LATICES OF HIGH SOLIDS CONTENT, ENABLE PREPARATION OF HIGH SOLIDS CONTENT LATICES OF GRAFTED OR FILLER EXTENDED OR FILLER-REINFORCED ELASTOMERS, ENABLE PREPARATION OF HIGH SOLIDS LATICES OF LOW MOLCULAR WEIGHT POLYMER WHICH ARE THEN MODIFIED TO MATERIALLY INCREASE THE MOLECULAR WEIGHT OF THE POLYMER, AND ENABLE THE PREPARATION OF IMPROVED STABLE LATICES BOTH DILUTE AND OF HIGH SOLIDS CONTENT, WHICH ARE USEFUL FOR EXAMPLE FOR ADHESIVE AND FILM FORMING PURPOSES. THE PROCESS IN COMMON WITH THAT OF RELATED COPENDING APPLICATIONSS IS CHARACTERIZED, INTER ALIA, BY THE ESTABLISHMENT OF A FLOW OF STEAM AS A CONTINUOUS PHASE INTO WHICH AN EMULSION OF A CEMENT OF THE POLYMER IS DISPERSED AS AN AEROSOL OF LATEX DROPLETS IN A SOLVENT-VAPOR CONTINUUM, FOLLOWED BY COALESENCE OF THE LATEX DROPLETS AND SEPARATION OF THE RESULTING COALESCED LIQUID PHASE FROM THE RESULTING SOLVENT-VAPOR PHASE. IN ONE EMBODIMENT OF THE PRESENT DISCLOSURE AN UNSABLE EMULSION IS PREPARED EMAEROSOL BEFORE COALESCENCE OF OVER 5% OF THE DISPERSED POLYMER PHASE OF THE EMULSION INTO DROPLETS OF GREATER PRESED PHASE OF WHICH IS ONLY TEMPORAILY OF PRECURSOR LATEX PARTICLE SIZE. THIS UNSTABLE EMULSION IS CONVERTED TO A STABLE LATEX BY PROVISIONS FOR DISPERSING THE SAME AS THE AEROSOL BEFORE COALESCENCE OF OVER 5% OF THE DISPERSED POLYMER PHASE OF THE EMULSION INTO DROPLETS OF GREATER THAN PRECUSOR LATED PARTICLE SIZE (OR FOR STABILIZING THE SAME BY THE ADDITION OF A SECONDARY EMULSIFIER TO THE SAME BEFORE SUCH CONDITION IS REACHED WITHOUT FURTHER REDUCING THE SIZE OF THE CEMENT DROPLETS OF THE DISPERSED PHASE), SO THAT THE LATEX IN THE AEROSOL AND SEPARATED THEREFROM IS KEPT FREE OF COAGULUM DURING THE COALESCING OF THE LATEX DROPLETS AND THE SEPARATION AND FURTHER TREATMENT, E.G. STRIPPING AND CONCENTRATING, WITH OR WITHOUT CORRELATED FURTHER ADDITIONS OF EMULSIFIER TO STABILIZE THE LATEX FOR STORAGE OR USE. THE SEPARATION OF THE GASEOUS AND LIQUID LATEX PHASE IS PREFERABLY EFFECTED WITH THE AID OF PARTIALLY CONCENTREATED LIQUID LATEX, AND IN CERTAIN EMBODIMENTS HEREIN DISCLOSED A MIXTURE OF SUCH PARTIALLY CONCENTRATED LATEX COMMINGLED WITH WATER VAPOR GENERATED THEREFROM IS ADDED TO AND COMMINGLED EITH THE AEROSOL BEFORE OR AFTER AT LAST A PART OF THE AEROSOL HAS BEEN COALESCED, AND THE COMBINED LIQUID PHASE AND COMBINED GASS PHASE OF THE RESULTING MIXTURE ARE THEREAFTER SEPARATED. ALSO IN CERTAIN EMBODIMENTS OF THE INVENTION A LIQUID FLOW OF SECONDARY EMULSIFIER MAY BE ADDED TO THE UNCLOSED OR PARTIALLY COALESCED AEROSOL, OR TO THE MIXTURE THEREOF WITH THE PARTIALLY CONCENTRATED LATEX, PRIOR TO THE SEPARATION OF THE GASEOUS AND LIQUID PHASE THEREOF.

Sept. 10, 1974 o. w..BuRKE, JR.

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*United States Patent 015C@ 3,835,061 Patented Sept. 10, 1974 U.S. Cl.252-359 A 14 Claims ABSTRACT OF THE DISCLOSURE The preparation ofaqueous latices from solvent dispersions of elastomers and other highpolymer compositions has presented problems including excessiveviscosity during processing and foaming and coagulation, which haveproduced losses and increased costs. Herein combinations of steps andapparatus are disclosed which reduce or eliminate various of theseproblems, especially coagulum; enable the preparation of latices of highsolids content; enable preparation of high solids content latices ofgrafted or filler extended or filler-reinforced elastomers; enablepreparation of high solids latices of low molecular weight polymer whichare then modified to materially increase the molecular weight of thepolymer; and enable the preparation of improved stable latices bothdilute and of high solids content, which are useful for example foradhesive and lm forming purposes. The process in common with that ofrelated copending applications is characterized, inter alia, by theestablishment of a flow of steam as a continuous phase into which anemulsion of a cement of the polymer is dispersed as an aerosol of latexdroplets in a solvent-vapor continuum, followed by coalescence of thelatex droplets and separation of the resulting coalesced liquid phasefrom the resulting solvent-vapor phase. In one embodiment of the presentdisclosure an unstable emulsion is prepared employing only a limitedquantity of emulsier, so that the homogenizing thereof produces anemulsion the dispersed phase of which is only temporarily of precursorlatex particle size. This unstable emulsion is converted to a stablelatex by provisions for dispersing the same as the aerosol beforecoalescence of over 5% of the dispersed polymer phase of the emulsioninto droplets of greater than precursor latex particle size (or forstabilizing the same by the addition of a secondary emulsiiier to thesame before such condition is reached without further reducing the sizeof the cement droplets of the dispersed phase), so that the latex in theaerosol and separated therefrom is kept free of coagulum during thecoalescing of the latex droplets and the separation and furthertreatment, e. g. stripping and concentrating, with or without correlatedfurther additions of emulsier to stabilize the latex for storage or use.

The separation of the gaseous and liquid latex phases is preferablyeffected with the aid of partially concentrated liquid latex; and incertain embodiments herein disclosed a mixture of such partiallyconcentrated latex commingled with water vapor generated therefrom isadded to and commingled with the aerosol before or after at least a partof the aerosol has been coalesced, and the combined liquid phases andcombined gas phases of the resulting mixture are thereafter separated.Also in certain embodiments of the invention a liquid How of secondaryemulsifier may be added to the uncoalesced or partially coalescedaerosol, or to the mixture thereof with the partially concentratedlatex, prior to the separation of the gaseous and liquid phases thereof.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a divisionof our co-pending application Ser. No. 784,596, filed Dec. 18, 1968(Pat. No. 3,644,263 issued Feb. 22, 1972) which was filed pursuant to arequirement for restriction there, and the disclosure of which is hereinincorporated by reference, said application Ser. No. 784,596 having beenan improvement over and continuation-in-part of our applications Ser.No. 621,997, filed Mar. 7, 1967 now Patent No. 3,503,917, and Ser. No.691,823, filed Dec. 19, 1967, and now abandoned, and Ser. No. 767,790,filed Oct. 15, 1968 (Pat. No. 3,622,127), the disclosures of which areherein incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention asa Whole relates to the production of high solids content aqueous laticeswith reduced polymer losses from solvent dispersions of high polymercompositions, and aims generally to provide improved method andapparatus combinations therefor, and new products produced thereby, andcertain of its novel apparatus aspects are claimed herein.

2. Description of the Prior Art To date, in the practical art, syntheticlatices of high polymers have been primarily prepared by emulsionpolymerization, and such practice has not been applicable to highpolymers made by essentially anhydrous catalyst polymerizations. It hasbeen proposed to prepare aqueous latices of high polymers from solventsolutions thereof by processes of the type which comprise the generalsteps of l) providing a dispersion or cement of the polymer in avolatile organic solvent for the polymer, (2) adding to such dispersionwater and an aqueous emulsier therefor and emulsifying the same toproduce an emulsion, (3) stripping the volatile organic solvent from thesaid emulsion, and (4) recovering the resulting latex product. However,in the practical art difficulty has been experienced in attempting torender such proposed processes commercially feasible, nter alia, in that(1) aqueous emulsication and stripping of solvent dispersions or cementsof the high polymer materials, especially when dilute, have yieldedlatices of only medium solids content at high viscosity which renderthem commercially impractical; (2) in that the emulsions have tended tofoam excessively during stripping; and (3) in that the emulsions havetended to form coagulum by coalescence of the polymer phase as well asby drying out especially ou contact with heated surfaces, durin thestripping and/or concentrating processes.

3 SUMMARY oF THE INVENTION When the molecular weight of a polymer ishigh, in order to form cements without excessive viscosity, whichprevents emulsiication of the cement, it is necessary to prepare thecements with low polymer and high solvent content. When these dilutecements are emulsiiied and then stripped of their high solvent content,the resulting latex contains an excess of emulsier and its latexparticles are very small. The excess of emulsier is undesirable in manyuses, e.g. in the use of the latex for producing latex foam. And whenthe average particle size of the latex is low, e.g. about 500 A., thenthe viscosity of the latex rises rapidly with increase in solids contentreaching 3,000 centipoises at 40% solids or less. It is usually thedesire of the industrial users of polymer latex that the polymer be ofhigh molecular weight, that the solids content be high, i.e. in therange of 50-70% that the viscosity of the latex be low (c g. not morethan 5,000 centipoises for adhesives, and as low as 1,000 centipoisesfor the production of latex foam products), and that the content ofemulsier be low. In various embodiments of the present invention, singlyand in cooperating combinations, provisions are made for attainingcertain of the above desiderata, particularly: (1) by providing a methodin which the precursor latex particle size of the cement in wateremulsions is controlled so as to obtain by an aerosol route latex ofsuch particle size (eg. in the range of 2,000 to 10,000 A., preferably3,000 to 5,000 A.) that they can be concentrated to have a solidscontent of over 50%, preferably over 60%, dry solids basis by weight,with a viscosity of not over 5,000 cps. at the 50% solids level, andpreferably not over that ligure at the 60% solids level; (2) byproviding such control by employing the precursor latex particle size ofan unstable cement-in-water emulsion, which emulsion is converted tolatex by the aerosol route without allowing it to coalesce to a point atwhich more than of the dispersed phase is in particles of greater thanprecursor latex particle size, and producing stabilization of theresulting latex either before, during or subsequent to the aerosolconversion and latex concentrating process.

In a rst embodiment of the invention, a latex is prepared from anorganic solvent dispersion of a composition of organic solvent solubleor dispersible polymer, the latex particles of which are of such sizethat the latex when at a concentration of 50% solids, dry basis byweight, has a viscosity no greater than 5,000 cps., and the latexcontains and is stabilized by an amount of cmulsier material in therange of 4 to 12 parts per 100 parts of the dispersed phase, by weight.In this embodiment the method comprises:

(a) providing a moving ow of gas comprising steam as an initialcontinuous phase,

(b) providing a cement consisting of a dispersion of the polymercomposition in essentially water-immiscible volatile organic solventwhich itself or as an azeotrope with water has a boiling point lowerthan that of Water at atmospheric pressure,

(c) emulsifying together said cement and water in the proportions of 0.5to 2.5 volumes of water per volume of cement with not less than 1A andnot more than 3A of the said amount of emulsier material based on thedry solids content of said cement, by weight, to form an unstableemulsion of temporarily precursor latex particle size,

(d) then, before coalescence of more than 5% of the dispersed phase ofsaid emulsion into greater than Y precursor latex particle size,dispersing the unstable emulsion of temporarily precursor latex particlesize into the ow of steam as the initial continuous phase and subjectingthe phases to a decrease of pressure while maintaining the temperaturethereof below the limiting temperature for maintaining the temporarystability of the emulsion, thereby vaporizing solvent from the disperseddroplets and forming an aerosol of latex in vapor,

(e) dispersing further emulsitier into said aerosol, to

the extent of at least one-fourth said amount of emulsiiier materialbased on the dry solids content of said cement, to stabilize the aerosoldispersed latex, and

(f) separating the stabilized latex from the vapor phase of the aerosol.

In this embodiment following step (f) the latex may be concentrated to asolids content, dry basis, of over 50%, by weight, preferably over 60%by weight, with a viscosity of not over 5,000 cps.

In a second embodiment of the invention, a latex is prepared from anorganic solvent dispersion of a composition of organic solvent solubleor dispersible polymer, the latex particles of which are of such sizethat the latex when at a concentration of 50% solids, dry basis byweight, has a viscosity no greater than 5,000 cps., and the latexcontains and is stabilized by an amount of emulsiiier material in therange of 4 to 12 parts per 100 parts of the dispersed phase, by Weight.In this embodiment the method comprises:

(a) providing a moving lovv of gas comprising steam as an initialcontinuous phase,

(b) providing a cement consisting of a dispersion of the polymercomposition in essentially water immiscible volatile organic solventwhich itself or as an azeotrope with water has a boiling point lowerthan that of water at atmospheric pressure,

(c) emulsifying together said cement and water in the proportions of 0.5to 2.5 volumes of water per volume of cement with not less than 1A andnot more than 3A of the said amount of emulsifier material based on thedry solids content of said cement, by Weight, to form an unstableemulsion of temporarily precursor latex particle size,

(d) then, before coalescence of more than 5% of the dispersed phase ofsaid emulsion into greater than precursor latex particle size,dispersing the unstable emulsion of temporarily precursor latex particlesize into the ow of steam as the initial continuous phase and subjectingthe phases to a decrease of pressure While maintaining the temperaturethereof below the limiting temperature for maintaining the temporarystability of the emulsion, thereby vaporizing solvent from the disperseddroplets and forming an aerosol of latex in vapor,

(e) separating the latex droplets from the vapor phase of the aerosol,

(f) concentrating the latex to a solids content, dry basis,

of over 50%, by weight, and

(g) dispersing further emulsifier into said latex, to the extent of atleast one-fourth of said amount of emulsier, after the dispersion of theemulsion in step (d) and before the concentration of the latex beyond45% solids, dry basis, in step (f).

In variations of this embodiment, the emulsiter material may comprise atleast two emulsiiiers, one having an aromatic nucleus and the otherhaving an aliphatic nucleus, and in a preferred species of thisembodiment a combination is employed in which the solvent is an aromaticsolvent, the polymer is an aliphatic polymer, the emulsilier employed instep (e) consists essentially of tially of emulsiiier having an aromaticnucleus, and the emulsiiier employed in step (e) consists essentially ofemulsitier having an aliphatic nucleus. Also in one species of thisembodiment step (g) is practiced prior to step (e), and in anotherspecies step (g) is practiced after step (e).

In a third embodiment of the invention, a latex is prepared from anorganic solvent dispersion of a composition of an organic solventsoluble or dispersible polymer, the latex particles of which are of suchsize that the latex when at a concentration of 50% solids, dry basis byweight, has a viscosity no greater than 5,000 cps., and the latexcontains and is stabilized by an amount of emulsier materials in therange of 4 to 12 parts per 100 parts of the dispersed phase, by weight.In this embodiment the method comprises:

(a) providing a moving flow of gas comprising steam as an initialcontinuous phase,

(b) providing a cement consisting of a dispersion of the polymercomposition in essentially water immiscible volatile organic solventwhich itself or as an azeotrope with water has a boiling point lowerthan that of water at atmospheric pressure,

(c) emulsifying together said cement and water in the proportions of 0.5to 2.5 volumes of water per volume of cement with not less than 1A andnot more than 3/4 of the said amount of emulsifier material based on thedry solids content of said cement, by weight, to form an unstableemulsion of temporarily precursor latex particle size,

(d) mixing into said unstable emulsion, before coalescence of more than5% of the dispersed phase of said emulsion into greater than precursorlatex particle size, further emulsiiier material to the extent of atleast one-fourth of said amount of emulsier material while maintainingessentially unchanged the particle size of the dispersed phase,

(e) dispersing the mixture formed in step (d) into the ow of steam asthe initial continuous phase and subjecting the phases to a decrease ofpressure while maintaining the temperature thereof below the limitingtemperature for stability of the emulsion, thereby Vaporizing solventfrom the dispersed droplets and forming an aerosol of latex in vapor,and

(f) separating the latex from the vapor phase of the aerosol.

In a fourth embodiment of the invention a latex is prepared, thedispersed phase of which is a composition of an organic solvent solubleor dispersible polymer, the latex particles of which are of such sizethat the latex, when at a concentration of 50% solids, dry basis byweight, has a viscosity no greater than 5,000 cps., and the latexcontaining sufficient emulsifier material to stabilize the same. In thisembodiment the method comprises:

(a) providing a moving ow of gas comprising steam as an initialcontinuous phase,

(b) providing a cement consisting of a dispersion of the polymercomposition in essentially water immiscible volatile organic solventwhich itself or as an azeotrope with water has a boiling point lowerthan that of water at atmospheric pressure,

(c) forming an unstable emulsion of temporarily precursor latex particlesize in two emulsifying steps, in the first of which said cement andwater are emulsified with sufficient emulsiier to form an unstable crudeemulsion, in which more than 5% of the dispersed phase droplets are ofgreater than precursor latex particle size, and in the second of whichsaid unstable crude emulsion is reduced to an unstable ine emulsionessentially of temporarily precursor latex particle size having no morethan 5% of its dispersed phase of greater than precursor latex particlesize,

(d) delivering said unstable line emulsion, as soon as it is formed insaid second emulsifying step, directly into said flow of steam as theinitial continuous phase and dispersing the same therein and subjectingthe phases t0 a decrease of pressure while maintaining the ternperaturethereof below the limiting temperature for maintaining the temporarystability of the emulsion, thereby vaporizing solvent from the disperseddroplets and forming an aerosol of latex in vapor,

(e) separating the latex droplets from the vapor phase of the aerosol,and

(f) concentrating the latex to a solids content dry basis,

of over 50% by weight.

In variations of this embodiment the emulsiier employed in step (c) isproportioned so that while only suicient to yield a temporarily stableemulsion of the cement, it is sufiicient to produce a stable latex ofthe polymer after removal of the solvent from the dispersed cementphase: or the proportion of emulsifier employed in step (c) issuliicient to produce only a temporarily stable latex of the polymerafter removal of solvent from the dispersed cement phase, and beforecoalescence of more than 5% of the dispersed phase of the latex intoparticles of greater than latex particle size, suicient additionalemulsitier material is dispersed into the latex to stabilize the latex,this step in certain embodiments being practiced after the dispersion'ofthe emulsion in step (d) and before the concentration of the latexbeyond 45% solids, dry basis, in step (f), and in other embodimentsbeing practiced by dispersing the additional emulsifier material intothe aerosol prepared by step (d) and separating the same from the vaporphase thereof with the latex droplets in step (e).

In its apparatus aspect the invention provides apparatus for removingsolvent from an aqueous emulsion of a solvent dispersion of high polymercement to form an essentially solvent-free, coagulum-free latex, theapparatus comprising, in combination, a conduit having a steam inlet, anemulsion inlet, and an aerosol outlet; means for delivering steam intosaid steam inlet-j; means comprising a homogenizer connected to saidemulsion inlet to deliver homogenized emulsion thereto fordispersion inthe steam ow therein tovform an aerosol of latex droplets as adiscontinuous phase in a solventvapor flow as a continuous phase; andmeans for withdrawing said phases `from said conduit; the homogenizerpreferably having its outlet connected directly to the emulsion inlet ofthe conduit; the homogenizer preferably being an ultrasonic liquid jetgenerator of the liquid whistle type; the emulsion inlet preferablyterminating substantially coaxially in the conduit in spaced relation tothe walls thereof, and most preferably in a nozzle arrangedsubstantially coaxially in said conduit, which may be of a preferredstreamlined form. In this iirst apparatus embodiment, the apparatus mayfurther comprise coalescing means for coalescing the tine liquiddroplets carried by the gas phase of the aerosol, said coalescing meanshaving aerosol inlet means and liquid and vapor outlet means, theaerosol outlet of said conduit being connected to the aerosol inletmeans of said coalescing means; and the vapor outlet means of saidcoalescing means being connected to the means for withdrawing saidaerosol phases from said conduit, and the said coalescing means maycomprise a tor-tuous path phase segregating means, or a centrifugalphase segregating means, or an axial impact phase segregating means.

According to a further embodiment of the invention, apparatus forremoving solvent from an aqueous emulsion of a cement which essentiallyconsists of a dispersion of high polymer in organic solvent, to form alatex, comprises, in combination:

(a) an aerosol generator having first and second inlets and an outlet,

(b) means for passing a flow of gas comprising steam as an initialcontinuous phase into said first inlet,

(c) a source of aqueous emulsion of solvent cement the solvent of whichitself or as an aqueous azeotrope has a boiling point lower than that ofwater, said source being connected to said second inlet `to deliver theemulsion of `cement to said generator for dispersion into the flow ofgas therein.

(d) means, e.g. valve means, for proportioning the ow of steam to saidfirst inlet and the flow of cement emulsion to said second inlet toprovide sulicient heat by condensation of steam in said ow to vaporizesubstantially all the solvent from the liquid phase into the gaseousphase of said ow while adding the condensate formed to said liquidphase.

(e) a separator having an inlet for mixed gas and liquid, an outlet forgas, and a separate liquid latex outlet, (f) a latex concentrator havingan inlet connected to said separate liquid latex outlet to receive a owof latex therefrom, and having an outlet, and comprising means forvaporizing a part of the water content of said latex -flow to convert itinto a flow of water vapor mixed with more concentrated latex and -tordelivering the same to said concentrator outlet,

(g) commingling means having an outlet and having inlet means and meansfor connecting its inlet means to the aerosol outlet and to saidcoucentrator outlet for mixing the gas and liquid phases of said aerosoland the water vapor and latex phases of said ow and delivering theresulting mixture of gas and liquid bodies from its outlet,

(h) means connecting the outlet of said commingling means to the mixedgas and liquid inlet of said separator, and

(i) means connected to the liquid outlet of said separator forwithdrawing latex therefrom.

In a preferred species of this embodiment, the means for connecting theoutlet of the aerosol generator to the inlet means of said comminglingmeans comprises coalescing means for coalescing the tine liquid dropletscarried by the gas phase of the aerosol, said coalescing means havingaerosol inlet means and liquid and vapor outlet means, the outlet ofsaid aerosol generator being connected to Vthe aerosol inlet means ofsaid coalescing means, and the liquid and vapor outlet means of saidcoalescing means being connected to an inlet of said commingling means.In further desirable species of these embodiments the means (h)comprises coalesciug means for coalescing the liquid droplets or bodiescarried by said flow and the liquid phase from said aerosol, saidcoalescing means having an inlet means connected to the outlet of saidcommingling means, and 4having an outlet means connected to the gas andliquid inlet of said separator.

Turning again to its process aspect, the invention as a whole provides aprocess for removing solvents from an aqueous emulsion of a cement whichis essentially an organic solvent dispersion of high polymer compositionto form a latex, which process comprises, in combination, the steps of:

(a) providing a moving flow of gas comprising steam as an initialcontinuous phase,

(b) providing a cement consisting essentially of a dispersion of notmore than 40% of the polymer composition in essentially not less than60% of Water immiscible volatile organic solvent which itself, or as anazeotrope with water, has a Iboiling point lower than that of water,

(c) forming from said cement and water and emulsier material an emulsionof at least temporarily precursor latex particle size,

(d) dispersing a iow of said emulsion as a discontinuous phase into saidow of steam as an initial continuous phase, in such proportion Ithatsuticient heat is provided by condensation of steam in said iiow tovaporize substantially all the solvent from the liquid phase into thegaseous phase of said ow, to form an aerosol while adding the condensateformed to the discontinuous phase of said aerosol,

(e) withdrawing a iiow of said aerosol,

(f) subjecting the withdrawn iow of said aerosol to a separation of itsydiscontinuous liquid phase from its continuous gaseous phase to form alatex,

(g) withdrawing a ow of said latex and subjecting said Awithdrawn flowof latex to vaporization of a part of its water content to convert saidflow into a W of water vapor mixed with bodies of more concentratedlatex,

(h) commingling the iiow produced by step (g) with the ow withdrawn bystep (e) and (i) subjecting the comminglcd flow produced by step (h) tostep (f) for eiecting separation of the liquid phase of said water vaporand latex flow from the vapor phase thereof simultaneously with thepractice of step (f), and

(j) withdrawing a part of the latex formed by said step And inparticular species of this latter process, the combination of stepsfurther comprises subjecting the flow of aerosol `withdrawn in step (e)to coalescing stresses to coalesce ne liquid droplets carried by thegaseous phase of the aerosol before subjecting said liow to thecommingling of step (h); and/or subjecting the commingled flows producedby step (h) to coalescing stresses to coalesce liquid droplets or bodiescarried thereby into larger droplets or bodies before subjecting thesame to step (f) in accordance with step (i).

In accomplishing the aforesaid objects, in respective embodiments of thepresent invention conditions are created combinations of which alleviatethe aforesaid problems and render practical the production of desirableaqueous latices from solvent dispersions of polymer compositions. Theseconditions, nter alia, include, severally and in various cooperatingcombinations in the several species of the invention, respectively:

(l) The use of particular solvents for the polymers which areessentially immiscible with water in liquid phase, and which haveboiling points less than the boiling point of water at atmosphericpressure, or which form azeotropes with water which have boiling pointsless than the boiling point of water at atmospheric pressure, andpreferably solvents which have boiling points higher than that of waterbut which form azeotropes iwith water that have boiling points lowerthan that of water, which preferred group comprises especially thearomatic solvents including toluene, the Xylenes, ethyl benzene, cumene,etc.

(2) The employment of ultradispersing equipment, in certain embodimentstogether with a homogenizer, eg. a homogenizer which forces the aqueousemulsion at a high pressure of 1,000 to 10,000 p.s.i. through aconstriction, or a homogenizer which forms an emulsion at anintermediate pressure of about 200 to 400 p.s.i. over the vibratingblade of the ultrasonic emulsator type, or a homogenizer of the highshear colloidal mill type, to reduce the polymer cement material in thepresence of the aqueous phase with a limited quantity of emulsier to theform of an unstable emulsion having its dispersed phase temporarily ofprecursor latex particle size preferably of sizes producing a latex ofrelatively narrow particle size distribution, and preterably one of anaverage size in the upper part of the colloidal size range. The saidconditions thus enable a primary quantity of emulsier to be employed toform the unstable latex of the desired particle size, which is largerthan the particle size obtainable when the emulsification and/orhomogenization is conducted in the presence of a stabilizing quantity ofemulsier material.

(3) The removal of solvent from tiny droplets of the so formed unstableoil-in-water emulsion by introducing the same, as a discontinuous phase,without allowing it to coalesce to a point at which more than 5% of thedispersed phase is in droplets of greater than precursor latex particlesize, into a ilow of gas comprising essentially steam as an initialcontinuous phase, and subjecting the two phases together to a decreaseof pressure while maintaining the temperature of both phases within thelimited range for stability of the aerosol carried latex phase. Solventis thus vaporized from the precursor latex sized particles whilemaintaining their stability, so that substantially all the solvent isvaporized into the gaseous continuous phase which thus becomes a gaseoussteam carrying aqueous droplets having one or more latex size polymerparticles per droplet, the preferred droplet size range being that of anaerosol of which the dispersed phase may comprise colloidal and largersized droplets in a steam/ solvent vapor continuum. For the purpose ofthis step the avoidance of coalescence above referred to may beaccomplished by dispersing the unstable emulsion into the tiow of steamto form the aerosol immediately after the homogenization, and preferablydirectly therefrom, so that insuliicient time elapses for suchcoalescence to occur. Alternatively, a stabilizing quantity of emulsier,i.e. a secondary quantity, may be mixed into the unstable emulsionWithout subjecting the same to conditions which would further reduce thedroplet size of the dispersed phase, to improve its stability and renderit unnecessary to convert it to the aerosol so quickly. The removal ofthe solvent from the cement particles, together with the aqueousdilution of the resulting latex particles, in some instances produceslatex particles which are sufficiently stable for separation from thegaseous phase and at least partial concentration, i.e. to not over 45%solids content, dry basis. When such condition does not pertain, inaccordance with this invention further emulsifier may be added to thedispersed phase of the aerosol by introducing liquid emulsitier oraqueous emulsifier solution into the aerosol as soon as it is formed,and before it is subjected to coalescing and separating of the liquidphase. In either event, it is preferred to add further emulsier to thelatex, preferably before concentration thereof has proceeded beyond 45%solids content, dry basis. If desired further emulsitier may be added tonally stabilize the high solids latex after the concentration thereofhas been completed.

(4) The separation of the resulting droplets of latex from the gaseouscontinuous phase by coalescing and collecting the same while avoidingdeleterious agglomeration and foaming, may be practiced in several wayswhich are quite distinct. One of these procedures employs centrifugalforce, which may be a number of times the force of gravity, to aid thecoalescence or segregation of the latex without foaming. A particularembodiment of this species subjects both the latex phase and the gaseousphase to centrifugal force under controlled pressure conditions, as in acentrifugal pump delivering from a region of higher pressure to a regionof lower pressure. Another procedure passes the two phases turbulentlyor tortuously through means dedining an elongated path to effect thecoalescence or segregation into droplets or bodies large enough to beseparated from the gaseous phase as hereinafter described. In otherprocedures such coalescences may be effected at least in part by adding,to the aerosol or partially coalesced aerosol, latex or partiallyconcentrated latex and vapor derived therefrom in eifecting such partialconcentration, such addition being made either before or after partialcoalescence of the liquid phase of the aerosol. The partially coalescedliquid phase from the aerosol and liquid of the added latex are thenready to be separated from the gaseous phase of the aerosol and thevapor, if any, introduced with the latex, to form a latex ready forfurther concentration. After the coalescence or segregation of theliquid phase in one of these manners, the resulting two phases arepassed to a collecting means, preferably of the cyclone separator type,and the gaseous phase is then passed to a condensing system from whichnoncondensibles are pumped by any suitable vacuum pumping means.Throughout the stripping, coalescing and collecting steps: (a) thetemperature of the two phases is maintained within the limitedtemperature range for stability of the emulsion during the period oftreatment, preferably by controlling the initial continuous phase intemperature essentially to not exceed such limiting temperature and inquantity to be sufficient to substantially etfect the stripping of thesolvent, and by controlling the temperature and quantity of the emulsionbeing dispersed therein; (b) the delivery of substantially all of thesolvent to the gaseous continuous phase can essentially be effected in asingle pass by appropriate design of the capacity of the apparatus, butmay be achieved in part in a rst pass through the stripping apparatusand be completed by an additional pass or passes of the partiallystripped material through the same or different equipment, e.g. by arecycle while concentrating, and (c) the ow of gas comprising steam asthe initial continuum preferably consists entirely of steam expanded,when it first contacts the emulsion, to sub-atmospheric pressure and toa temperature not detrimental to the latter, where any substantialquantity of solvent is being stripped from the precursor latex sizedparticles, but, under conditions where it is desired to augment thevolume or velocity of the initial continuum, being augmentable byincluding a minor proportion of non-condensible gas or of the solvent inthe said flow of gas, for which purpose a minor proportion of theeffluent gas phase from the separator, or of the azeotrope remaining insaid gas phase after condensation of unazeotroped water vapor therefrom,may be recycled to constitute a part of the initial continuum, or inparticular embodiments, by the introduction of only a part of the steamat the point at which the emulsion is injected, and augmenting the flowand solvent vaporation by the introduction of further steam downstreamfrom the point of emulsion introduction.

(5) The latex delivered by the separator may be recycled and be againpassed through the centrifugal segregator or the elongated pathsegregator either separately or after commingling with the aerosol orpartially coalesced aerosol, and in such recycling the latex beingrecycled may be passed through a heat exchanger to convert it to a ow oflatex bodies carried along by water vapor generated from the latex, thusto concentrate the latex by removing Water therefrom, when a product ofhigher solids content is desired. When concentrating stripped latex onemay cut off the supply of initial raw emulsion and the steam and supplythe external heat to the latex through the Walls defining the elongatedpath, e.g. a plate heat exchanger, to vaporize water from the latex withthe aid of reduced pressure and may separate the water vapor and latexin the same vacuum separator. Where it is advantageous to remove solventand concentrate the latex continuously then separate equipment units maybe coupled together, one unit for stripping of the solvent from the rawpolymer-solvent emulsion with or without latex recycling, and the otherunit for concentrating of the stripped latex. The concentrated latexefuent as a discontinuous phase from the heat exchanger with the evolvedwater vapor which is at least a part of the continuous phase, may againbe separated in the separator, the vapor phase passing to the condensingequipment, and any uncondensables again passing therefrom to the vacuumpumping equipment.

(6) While for economy of equipment it is sometimes preferred to employthe same segregator, with adjustment of appurtenant equipment as abovedescribed, for effecting both the stripping and the concentration, thecapacity of the segregator may be adjusted to the load to be served, andwhen it is desired to concentrate the stripped latex without suspendingthe stripping operation of the equipment, one or more separate ormerging elongated paths or the like'may be provided for 1 1 thispurpose, which may terminate in any desired separator equipment. Thedesired concentration may be effected in a single pass, or, if desired,in a plurality of recycles through the same or different concentratingpaths. When the latex being concentrated is returned to the samesegregating, separating, or collecting equipment, it is preferablydistributed on the walls of the segregator, separator, or collector insuch a way that the droplets or bodies of stripped latex being deliveredthereto With the solvent vapor Will be impinged on the recycled latex,as it has been found that this procedure tends to minimize the formationof coagulum and foam.

(7) The water recovered in the condensing equipment is distilled watersaturated with the stripped solvent, and it is preferred to recycle thisrecovered water for use in preparing the unstable emulsion of theprecursor latex sized particles of solvent solution of the high polymercomposition.

'(8) Various of the above conditions are common to embodiments ofprocess disclosed in the aforesaid copending applications, and variousadditional features and combinations of features therein disclosed to bemore particularly adapted to cooperate with various of the aforesaidfeatures to effect modification of the physical and/or chemicalcharacteristics of the latex produced and/or to facilitate theoperations for produring the same, can be employed in conjunction withthe present invention, which (a) enables one to control the precursorlatex particle size of the emulsion supplied to be stripped of solventto facilitate the processing operation and reduce polymer losses whileproviding a latex concentrated or concentratable to a high solidscontent, preferably 60 to 68% solids, dry basis, and/or to improve theseparation of the gas and liquid phases of the aerosol by adding liquidlatex to and commingling it With the aerosol as a part of the coalescingseparation before subjecting the resulting mixture of `gas and liquidphases to separation.

The objects of the invention, severally and interdependently, are toprovide new yapparatus features and new combinations of steps, whichcontribute to produce an improved process and which enable theproduction of new latices which may contain not only polymers andcompounding ingredients such as fillers, but which in preferredembodiments may contain such compounding ingredients, c g. reinforcingfillers, within the high polymer latex particles. Other objects andadvantages of the invention will be apparent from the above generaldescription and the following more particular descriptions of preferredembodiments thereof, which, however, are illustrative but notrestrictive of the invention, the scope of which is more particularlypointed out in the appended claims.

By the term latex as used herein is meant an aqueous suspension ofcolloidal polymer particles and emulsier material and the polymerthereof may be selected from the following types and combinationsthereof:

(i) homopolymer,

(ii) interpolymer including block and graft polymer,

(iii) hydrocarbon polymer,

(iv) polar polymer,

(v) cross-linked polymer,

(vi) non-cross-linked polymer,

(vii) polymer composition comprising polymer material selected from (i)through (vi) above and compounding ingredients including reinforcingfillers and/ or non-reinforcing fillers.

By the term colloidal particle or colloid as used herein is meantparticles in the size range of 500 A. to 10,000 A. diameter, and by theterm upper portion of the colloidal size range is meant particles in thesize range of above 2,000 A., preferably 3,000 to 5,000 A. diameter.

12 BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. l is a flow sheet or diagram illustrating the sequences of stepsand flow of material in typical embodiments of process according to theinvention.

FIG. 2 is a diagram of a preferred form of equipment for preparing theemulsion, corresponding to portions 7-13 of FIG. l, the correspondingelements having the same numerals raised by 100, and respective partsthereof being designated by modifying letters.

FIG. 3 is a similar diagram of a preferred form of device for dispersingthe emulsion of solvent/polymer cement into the steam flow, andsegregating and separating the latex phase from the vapor phase, andfurther treating the latex phase, corresponding to portions 14 andfollowing of FIG. l.

FIG. 4 is a more or less diagrammatic elevation partly cut away of apreferred embodiment of the portion 14 of FIG. 1.

FIG. 5 is a more or less diagrammatic elevation, partly cut away, of apreferred form of separator corresponding to portion 16 of FIG. 1.

FIG. 6 is a more or less diagrammatic horizontal crosssection taken online VI-VI of FIG. 5.

FIG. 7 is a more or less diagrammatic elevation partly cut away of apreferred arrangement comprising a solventcement aqueous emulsionhomogenizer delivering its output directly to an aerosol generator,according to the invention.

FIGS. 8 to 11 are diagrammatic flow sheets indicating modes of admixingpartially concentrated latex, with or without water vapor evolvedtherefrom, with the gaseous and liquid phase from the aerosol generator,for aiding in the segregation and separation thereof.

FIGS. l2 to 15 are lvertical elevations partly cut away of types ofmixer nozzles or in line mixers employable as aerosol generators and/ormixers in the practice of the invention, e.g. in FIGS. 8 to 11.

FIG. 16 is a more or less diagrammatic elevation of another embodimentof the invention.

DESCRIPTION OF PREFERRED yEMBODIMENTS (a) In General In the preferredembodiments illustrated in FIG. 1, the high polymer (1), e.g. elastomerand/or plastomer material as hereinafter described, is prepared as ahigh polymer composition (4) for conversion to a cement, as by workingin appropriate masticating, comminuting, or attenuating equipment (2),such as a rubber mill, Banbury, comminutor, extruder, or the like. Inaccordance with the aforesaid applications provision may be made forincorporating one or more known polymer compounding ingredients (3),e.g. rubber reinforcing filler, into the said polymer composition insuch a way that the ingredients (3) are thereafter contained Within -thepolymer particles of the latex being formed, for which purpose the saidingredient or ingredients (3) may be worked into the high polymer (1) byWorking therewith in the masticating equipment (2). By such procedurethe Said polymer ingredients may become fixed to the compoundingingredient, i.e. the polymer particles can become reinforced by thefillers, and in etect become so intimately attached thereto, orembrasive thereof, as to retain the same when dispersed as a cement. Inthecase of compounding ingredients desired to be incorpoarted in thelatex particles, but not requiring working with |the polymer itself,such ingredients (3) may be fed into the cement forming equipment ordissolver (5) independently of the said polymer composition (4), as isalso indicated in FIG. l.

In the cement forming equipment or mixer or dissolver (S) which may alsocomprise a disperser, the high polymer composition (4) is combined andpreferably stirred or otherwise Worked with solvent (6) appropriate forthe high polymer and for the process, as further described herein, toform a solvent cement (7 of the high polymer composition (4) and of anyextraneously added compounding ingredients (3), the adequate dispersionof which in the cement may require vigorous working, which may even beaccomplished by the passage of the cement through a suitable dispersingequipment (7a).

The solvent/polymer cement (7) is then combined with emulsier (8)appropriate for the high polymer and the process, and with water (9) ina coarse emulsion mixing equipment (10) where the ingredients are mixed,preferably with the aid of heat, to form a coarse cement in wateremulsion (11), which is then passed one or more times through anultradispersing equipment (12), preferably of the type hereinafterdescribed, which breaks up the relatively large particles ofsolvent-cement forming the discontinuous phase in the coarse emulsion(11) into particles of precursor latex size, i.e. which will be of atleast temporarily stable latex particle size when relieved of theirsolvent content, and preferably in the upper portion of the colloidalsize range.

As in my aforesaid applications the coarse cement-inwater emulsion (11)may be passed one or more times, usually 6 to 12 times, through one ormore so-called ultra-dispersers (12) of the Moulds type more fullydescribed hereinafter, in order to accomplish a suicient reduction oflatex particle size. The resulting fine emulsions have rather wideranges of cement droplet size distribution and adjusted if necessary toan appropriate temperature, as by the cooler 13A, by-pass 13B and/orheater 13C, may be fed by suitable positive displacement, e.g. plunger,pump means 13D, to a homogenizer 13E, preferably of the vibrating bladetype or of the resiliently restricted orifice type operating atpressures in the range of 1,000 to 10,000 p.s.i., for reducing theparticle size distribution of the fine emulsion. The resulting emulsion13 of reduced particle size distribution with or without cooling by acooler 13F is preferably delivered directly to a steam mixer or aerosolgenerator 14 where it is dispersed into a lflow of steam as hereinafterdescribed. As indicated in FIG. 1 the emulsiier material (8) may beformed into an aqueous emulsier solution (8') with Water (9') saturatedwith solvent or with water (9) from an extraneous source.

The resulting ne cement-in-water emulsion 13, in accordance withpreferred embodiments of the present invention is an unstable emulsionof only temporarily precursor latex size particles, and in suchpreferred embodiments of the present invention is either stabilized asby adding further emulsifier at 8A1 before further treatment or,preferably, is immediately converted into an aerosol, of which thedispersed phase may comprise colloidal and larger sized droplets in asteam/solvent vapor continuum, before agglomoration of over of itspolymer-solvent particles into greater than precursor latex particlesize, and is therein stripped of its solvent content. In such aerosolform the stripping is accomplished without excessive foaming and whileavoiding formation of coagulum, desiderata which cannot be attained whenany substantial proportion of solvent is attempted to be removed from anaqueous emulsion of high polymer solvent cement in other than an aerosolcondition. As in the aforesaid applications, the formation of theaerosol is preferably accomplished by providing a flow of steam (14a) asan initial continuous phase and introducing the oil-in-water emulsion ofat least temporarily precursor latex sized particles (13) as adiscontinuous phase into the ow of steam as the initial continuous phasein a mixer or aerosol generator (14), whereby volatile solvent (6) isvaporized to become the continuous phase or the principal part thereof,and a corresponding amount of steam is condensed to supply the heat ofvaporization for the solvent and become added as water to thediscontinuous phase. As explained in connection with FIGS. 3 and 4, incertain embodiments of the present process a part only of the steam maybe supplied at a first station where the emulsion of polymer/ solventsolution is introduced, and the remainder of the steam may be introducedat one or more stations downstream from said iirst station. As the phasetransition is accomplished the resulting gaseous and non-gaseous phasesare usually in a forrn resembling an aerosol and the aerosol dropletsare then coalesced to form a latex separable from the vapor phase. E'venwhen the emulsion has been prepared with only a limited quantity ofemulsiier and has its dispersed phase only temporarily of precursorlatex particle size, the latex produced by the phase transition in theaerosol may be suiiciently stable for coalescence or even forconcentration. When these conditions do not pertain liquid emulsier orliquid emulsifier solution may be added to the aerosol produced in theaerosol generator 14, as at 8A2.

The coalescing step may be practiced by passing the gaseous andnon-gaseous phases through a coalescing means 15 in the form of asegregator or coalescer while maintaining the temperatures of the flowswithin the limited range for stability of the latex, and the coalesceddroplets, now definitely of greater than aerosol size, are collected inthe form of a bulk latex from the gaseous continuous phase. As is morefully described in connection with FIG. 3, in certain embodiments of thepresent invention, the coalescing is accomplished by subjecting theaerosol, on its way to a reduced pressure separator 16, to the action ofcentrifugal force for effecting segregation or coalescence of thenon-gaseous phase, as by passing the gas and latex phases of the aerosolthrough a centrifugal pump, and preferably a centrifugal pump having thetype of pump rotor, pump chamber and inlet and outlet means illustratedin U.S. Pat. No. 3,324,798. As is also more fully described inconnection with FIG. 3, in lieu of the centrifugal segregator, othertypes may be employed, c g. a plate-type tortuous path segregator or anaxial impact phase segregator. The nal separation or collection may beattained by delivering the flows from the segregator (15) into aseparator or collector (16), from the lower part of which the latex isdrawn, and from an upper part of which the continuous phase is passed tocondensing equipment (17) maintained under vacuum, preferably a vacuumof the order of 28 to 29 inches of mercury, by withdrawal of uncondensedgases therefrom by vacuum pumping equipment (18), e.g. a steam jet, andthe separator of collector (16) may be of various forms and may even beincorporated with a segregator (15) as is described in said copendingapplication Ser. No. 691,823.

Still referring to FIG. 1, the high polymer composition latex (19)withdrawn from the separator (16) may be delivered as product (20), ormay be recycled as indicated at (21) and be again fed as discontinuousphase through the steam disperser (14) and/or the segregator (15) forremoval of residual solvent therefrom as above noted, either separatelyor concurrently with additional emulsion (13) as is indicated by thevalve symbols between (13) and (14) and in the lines from (16B) to (14)and in the lines from (16B) to (14) and from (16B) to (16) in FIG. 1; orit may be cycled through a different or the same heater and separator(21 and 16) for concentrating the latex, in which event the latex isheated to evaporate water therefrom under sub-atmospheric pressure attemperatures within the limited temperature range for its stability, byheating fluid passing externally to its flow path (in 21) from thevalved heat sources shown connected to (15) and (21), while the supplyof steam internally of the path from the valved source (14a) is reducedor cut 01T as aforesaid. When such concentrating step has been employed,the product (20) resulting therefrom will be a latex of increased solidscontent.

The present invention, however, makes provisions which may be employedfor modifying the latex 20. These provisions are illustrated at 24 andfollowing in FIG. 1

herein. Thus, in these embodiments of the invention, the latex ofintermediate solids content may be mixed in a hold tank, mixer, orproportionate feeder 24 with polymerization catalyst 24a and monomermaterial 24b, and after appropriate adjustment of its temperature, as bya heat exchanger means 25, may be passed to polymerization reactor means27. The modied polymer latex delivered by the reactor with or Withoutadded emulsiiier (8A4) may be delivered to storage 29, preferablythrough a cooler 28, pending delivery as by a pump 30 for furthertreatment in heating and separating apparatus 31 and 32, which may be ofthe type shown at 1220 and 1216F in FIG. 3, hereinafter described. Inthis further treatment residual solvent, odors, and unreacted monomer,if any, may be removed, and if desired the latex may be furtherconcentrated. The modified latex from separator 32, which in each eventwill have, along with other modications, a higher solids content thanthe latex 20, may be passed by a pump 34 to product storage 36,preferably through a cooler 35.

In certain embodiments of the invention, the operations up to point maybe conducted to form the cement and latex 20 of low molecular Weightpolymer, which enables a cement of higher solids content to be employedWithout having to deal with excessively high viscosity, and monomer 24hand catalyst 24a, and temperature in the apparatus 27 may be employed insuch quantities and degree as to materially augment the molecular weightof the polymer, and especially when it is desired to highly augment suchmolecular weight, polymer crosslinking agent 24C may be added in themixer 24, for intimate association and reaction in the apparatus 27.

The final stripping, de-odorizing, and/or conentrating in separator 32is preferably effected as shown with the aid of condensing equipment 37and vacuum pumping apparatus 38, and When such equipment produces ayield of recoverable iluid, c g. pure water, such may be returned forreuse, e.g. to the water supply 9, as shown. Where prolonged shelf lifeis desired, additional emulsilier may be added to the latex from SAS,preferably ahead of the pump 34.

In a still further embodiment of the invention, exemplied in FIG. 3, thestripped latex 324 still containing residual solvent, is subjected toconcentration, deodorizing, and stripping of residual solvent in aheating apparatus 1220 and separator 1216, and is then, as a finishedhigh solids latex, subjected to heating to an appropriate temperature at1225, and further treatment with polymerization catalyst 1224a andmonomer material 12241) and/or cross-linking agent 1224c for effectinggrafting or crosslinking of the polymer molecules contained in theparticles of the finished latex. When necessary after this treatment,the grafted or cross-linked latex may be stripped of residual volatilesand odor, as by passing it through a stripper-deodorizer-concentratorcircuit, which may be the same circuit 1220-1216 isolate for thispurpose as by opening valves 1227a and 1229 and closing valves 1228 and1231. Delivery of the treated latex to storage 1233 is preferablyeffected after cooling in a heat-exchanger 1232, by appropriateadjustment of the valves 1227a-123L (b) The Polymer Material (1) The newprocess is applicable to the preparation of latices from solventsolutions or dispersions of polymer materials which are essentiallysolvent soluble or dispersable and essentially water insoluble,including natural rubber and polymers of ethylenically unsaturatedmonomer material containing from 2 to 20 carbon atoms, preferably from 2to 10 carbon atoms. It is especially applicable to those elastomers andplastomers which, with or without plasticizers, have the foregoingproperties and properties adapting their latices for use as adhesives,binders, lm forming materials, coating materials, etc. Examples of suchelastomers and plastomers, illustrative but not restrictive of those towhich the invention can be applied, are set forth in my aforesaidantecedent application Ser. No. 784,596 (Pat. No. 3,644,263) and areherein incorporated by reference.

(c) COmpounding Ingredients (3) (3a), (1223a) The compoundingingredients which are especially contemplated in the present inventionare the solid, particulate, compounding ingredients which are insolublein the solvents (6), namely: llers, including rubber reinforcingfillers, pigments, etc., which by the present invention may beincorporated into the polymer composition particles of the latices,rather than merely in the water phases thereof. The solid particulatecompounding ingredients of this class comprise those set forth in saidantecedent application, and herein incorporated by reference.

(d) The Emulsiliers (8) (8')(8A) etc.

The invention in its broader aspects is not dependent on the use of anyparticular emulsifier or combination of emulsiiers, and may be practicedwith any selected emulsifier or emulsitier combination suitable foraqueously emulsifying and stabilizing the non-aqueous solvent solutionsor dispersions of the polymer materials concerned, and/ or forstabilizing the latices derived therefrom in the aerosol generator, orfor subsequent treatment or conditioning, for which purpose the emulsieror combination of emulsiiers must be Water soluble or water dispersible.Suitable emulsiers are set forth in said antecedent application (Pat.No. 3,644,263) and are herein incorporated by reference.

(e) Monomer Materials (241)), (122412) The ethylenically unsaturatedmonomer material employable herein is selected from the class set forthin said antecedent application (Pat. No. 3,644,263) and hereinincorporated by reference.

(f) Free-Radical Generating Polymerization Catalysts (24a), (1224a) Thefree-radical generating catalysts and catalyst systems useful in therange of 0.8 to 20 parts per 100 parts of added monomer materialsemployed in certain embodiments of the present invention constitute awellknown class which is set forth in my said antecedent application(Patent No. 3,644,263) and is herein incorporated by reference.

(g) Cross-linking Agents (24C), (1224c) The cross-linking agents useful,in the range of 0.1 to 20 parts per 100 parts of polymer content of thelatex by weight, for effecting the cross-linking employed in particularembodiments of the present invention, also form a wellknown class ofmaterials which is set forth in my said antecedent application (Pat. No.3,644,263) and is herein incorporated by reference.

(h) Ionizing Radiation The ionizing radiation employed in certainembodiments of the present invention is of a type known to those skilledin the art, and set forth in my said antecedent application (Pat. No.3,644,263) herein incorporated by reference.

(i) Equipment Homogenizers.-While the invention in its broader aspect isnot limited to any particular homogenizer, the invention has disclosedthat certain types of homogenizer described in Mould, Jr. Pat. No.3,195,867* and Hager Pat. No. 3,194,540* as suitable for low viscositymaterials such as milk, oil, fruit slurries, etc., can be employedeffectively as an ultradisperser of aqueous emulsions of higher viscoussolutions of polymer compositions, especially when connected in tandem,and/ or for recycle, and in particular that a combination of such Mouldtype homogenizers followed by a resiliently restricted orifice type highpres- 17 sure homogenizer (1,000 to 10,000 p.s.i.) e.g. of the Gaulintype (see Gaulin patents Nos. 753,792* and 756,953* as available fromManton-Gaulin Mfg. Co., Inc., as model K24-3BS but provided with a 75horsepower motor, provides an aqueous emulsion of solvent/polymer cementyielding a latex having latex particles of an average diameter near theupper end of the colloidal size range suitable for high solids polymerlatices, and of relatively narrow particle size distribution, whenprocessed according to the invention.

In FIG. 2 there is shown an arrangement of such Mould type and Gaulintype homogenizers to constitute a preferred cement emulsifyingequipment. This arrangement is provided with optional facilitiesselectively employable by means of valves for continuous or batchoperation, for single unit or tandem unit operation, and for selectivecomplete or partial recycle in each mode of operation, and it will ofcourse be understood that where certain of these optional facilities arenot desired they may be omitted without departing from the invention.

In this FIG. 2 arrangement the solvent and polymer dispersion 107 andthe water and emulsiiier solution 108 are adjusted in temperature byheat exchangers 110A and passed to the coarse emulsion mixer equipment.For batch operation, as shown, this equipment may be in the form of ahold tank 110 provided With an agitator. For continous operation, asshown, it may be in the form of inline mixing equipment 110B'. Thein-line mixer equipment 110B may also be employed to premix thematerials being delivered to tank 110 for batch operation. The coarseemulsion in batch operation is passed from tank 110 under gravity headand/ or pressure head contributed by pump 110C to the ultradispersingequipment 112 and/ or 112A and/or 112B, or for continuous operation maybe passed to the latter directly from the in-line mixer equipment 110B,and under the head developed thereby augmented, if desired, by the headdeveloped by pump 110C. The coarse emulsion under pressure as aforesaidmay be passed through any one of more of the ultradispersing equipments112-112B and may be recycled therethrough either directly, or by way ofthe coarse emulsion tank 110. When the preparation of the emulsion ofprecursor latex sized particles has been completed this intermediateproduct may be delivered to storage 113, preferably being cooled bymeans of a cooler 113F to assure maintenance of the emulsion even withminimum quantities of emulsifying agent present. As is indicated in FIG.2, effective results have been attained by repeatedly passing the coarseemulsion through an equipment 112 of the perforated stator type shown inMould, Jr. Pat. No. 3,195,- 867, and then through one or more equipments112A and/ or 112B in tandem with, and similar to, equipment 112 butprovided with a slotted stator of the type illustrated in FIGS. 5 and 7of Hager Pat. No. 3,194,540, with recycling from equipment 112A to thetank 110 and then by gravity head through equipments 112 and 112A, abouta half dozen to a dozen times before delivery of the resulting productto the storage tank 113. During recycling, especially with sensitiveemulsion prepared with a minimum of emulsifying agent, it is desirableto cool the emulsion which has been heated by working in theultradispersing apparatus, by means of a heat exchanger in the recycleline, as at 112C.

After the emulsion has been reduced to unstable emulsion of precursorlatex particle size, when this feature of the invention is employed, afurther amount of emulsier may be combined therewith as shown at 113g7is FIG. 2 by simple mixing as in mixer M in the lines leading to 113F,without further homogenizing action that would further reduce theparticle size of the dispersed phase. The emulsion of at leasttemporarily precursor latex particle size in the desired range may befed, when stable or stabi- *Heren incorporated by reference.

lized, to storage `113 or 113]', or, when only temporarily stable may befed directly to the mixer or aerosol generator of FIG. 3 via valved line113k or valved line `113i As is further shown in FIG. 2, various typesof homogenizer can be employed for forming the tine emulsion of cementat least temporarily of precursor latex particle size, e.g. ahomogenizer of the colloid mill type 213, a homogenizer 313 of thevibrating blade type such as the liquid whistle or 'Rapisonic(trademark) types '(presently preferred when used as in FIG. 7), or anemulsiier of the high pressure resiliently restricted orice type 113D,113B to which the emulsion efHuent from Vthe ultradispersers 112-112B isfed after heating, e.g. to temperatures of l40-160 F. by the heat of113A. The Gaulin type homogenizer comprises the pump 113D which is aplunger pump that develops from 1,000 to 10,000 p.s.i. depending on theresilient load applied to the valve head means resiliently restrictingthe emulsifying orifice or valve-opening means of the device. This loadcan be adjusted in the commercial devices by means of a hand wheel,shown at the entrance end of the homogenizer 113E. The output from theunit 113B may be delivered to cooler 113F and thence to storage 113]',or via 113h or may be stored in tank 113 when recycling through thehomogenizer circuit 113D-113F is desired.

Stripping Mixer.-The stripping mixer 14 (FIG. 1) which disperses theaqueous emulsion of precursor latex sized solvent/polymer droplets intothe gaseous stream of steam is preferably of the type illustrated inFIG. 4, consisting of a conduit section 114, which may be transparent,which has supported centrally thereof a torpedo shaped or tid-shapedmember 114A for producing a restricted or venturi-effect passage 114Bthereabout. The initial continuous phase of steam is admitted as at 114Cto flow through the passage 114B and produce an area of high velocityand low static head thereat. The aqueous emulsion of solvent/polymersolution is introduced into the central body 114A as by way of the tube114D upon which it is supported, and issues into the gas stream via anarrow slot 114E extending peripherally of the body 114A at the regionof greatest pressure reduction in the space 114B. Auxiliary steam and/oremulsier may be introduced at 114F and 114G. As a rule only a very minorproportion of the steam, if any, will be admitted at 114F or 114G, as itis important to have the quantity of steam admitted at 114C suicient inheat content to vaporize substantially all the solvent from thedispersed phase Of the aerosol produced in the space 114B. When thiscondition is attained, as observed through the transparent conduitsection 114 the surfaces bounding the annular and cylindrical passagethrough the conduit 114 remain free of liquid or solid materials and nofoaming can be seen. The aerosol droplets thus attain a size so smallthat the volume of emulsion therein is too small to form a bubble onvaporization of solvent from the solvent-polymer particles dispersedtherein. The fact that the solvent-stripped particles of the aerosol andsteam condensate remain in contact with the solvent-vapor phase ofcourse establishes a vapor pressure equilibrium therebetween and thedispersed phase of the aerosol thus contains residual traces of solvent,e.g. of the order of 1% or less, which it is desirable to remove as faras possible with the latex in a dispersed condition rather than a bulkycondition prone to foam on evolution of vapors therein. The outlet ofthe aerosol generating section 114 connects to the vacuum equipment byway of the segregator and collector devices, as exemplied in FIGS. 3 and5, and the vacuum in the chamber 114 is such that the temperaturesattained do not exceed those at which the emulsion and latex are stable.As above noted, the heat for vaporization of the s01- vent from thesolvent/polymer solution is for the most part derived from thecondensation of the steam, and the flowing stream of steam and organicvapor carrying the resulting suspended latex droplets is in the natureof an aerosol, exhibits no foaming in the tube 114, and does not 19'coat or foul the tube 114. As is illustrated in FIG. 3, the aqueousemulsion of solvent/polymer solution is usually supplied to the mixer114 under pressure, as by a pump 114H.

Coalescing and Separating Means Separating the latex from the aerosol iseffected herein by a combination of coalescing means for coalescing thedispersed latex droplet phase of the aerosol into larger droplets orbodies of latex in the presence of the solventvapor gaseous phase, andmeans for then separating such larger bodies of latex from thesolvent-vapor gaseous phase. In the present application and theaforesaid co pending applications various forms of coalescing andseparating means are disclosed, exemplified herein, e.g., by thedelivery of the aerosol from the aerosol generator and stripper 114(FIG. 3) through coalescing means 115, 215, or 315 to the hereinaftermore fully described evacuated cyclone separator means 216, which ispreferably internally coated by a sheet of recirculated liquid latexsupplied via conduit 216F or conduit 216G and liquid distributor 216A.The coalescing means 21S is a plate type tortuous path segregator whichkeeps coalescing the liquid phase by impingemeiit, and breaking anybubbles formed therein by impact, as the latex and gas progress down thetortuous path along the pressure gradient to that of the separator 216,and delivers the coalesced bodies of latex and gas to the separator 216.The coalescing means 115 is shown as a centrifugal segregator in whichthe coalescence is effected by centrifugal force, e.g. a centrifugalpump operating with cavitation and fed with the aerosol, and isrepresentative of similar centrifugal coalescers illustrated in thesecond and third of my aforesaid copending applications. And thecoalescing means 315 is typical of means wherein the aerosol isprojected against an impact surface 315A to effect coalescence of theliquid phase impinging thereon when the gaseous phase is deflectedthereby, and when the impact surface 315A is arranged coaxially of theaerosol inlet and rotated by a suitable motor 315B, as shown, thecoalesced liquid may be centrifugally discharged against the annularsurrounding wall 315C and may be withdrawn separately from the gas phasevia separate conduits 315D and 315B, respectively, the discharge to thelatter being from behind the surface 315A in the form shown. In thislatter case, as in the case of FIG. 4 of copending application Ser. No.691,823, the conduits 315D and 315B may both discharge into theseparator 216 either directly or with the liquid delivered by way of therecirculating circuit 216G as shown; or as illustrated in FIG. 16herein, the separator 216 may even be omitted in some instances, Wheresufficiently low carryover of latex in the gas via 315B (11156) enablesthat conduit to be connected directly to the condenser vacuum systemthus converting the unit 315 (1115) into a combined coalescer andseparator as shown in FIG. 16.

Separating, Condensing, and Evacuating Apparatus As will be apparent tothose skilled in the art the invention in its broader aspects is notdependent on the use of any particular type of separating, condensingand evacuating apparatus. Conveniently, when stripping azeotropingsolvent, in the arrangement of FIGS. 1 and 3 as a separator or collector16 (216) may be used a vertical cylindrical receiver, with a downwardlytapering bottom leading to a discharge opening connected to a positivedisplacement pump for removal of separated latex therefrom lwithoutbreaking the vacuum, with a tangential side opening for passage of thetwo flows thereinto, and with a top opening for the discharge of thecontinuous phase to the condensing equipment. The latter convenientlymay comprise two condensers, one for non-azeotroped water, and the otheroperating at a lower temperature for azeotrope of water and solvent. Theevacuating apparatus conveniently may comprise a steam jet evacuationequipment connected to draw non-condensed material from the condenserequipment, or a vacuum pump.

In the form shown in FIGS. 3, 5 and 6, the collector 216 generallyresembles a cyclone collector into which the gaseous -flow and any latexdroplets carried thereby are discharged tangentially from the inlet215H, and guided along the Walls by appropriate internal baliiing, e.g.,the spiralling skirt 216D, so that the liquid collects on the walls andliows to the bottom outlet 216C, While the gas passes to the top outletby the way of the passage afforded by the central drop tube, orequivalent baiing means, 216D to the condensor/vacuum system. Pump`means 216B delivers the latex from the outlet 216C through the outletvalve 216B and, depending on pump and valve setting, Wholly or partlyvia the recycle lines 216G, 216L. Valve 216M can be a pressure Openedrelief valve for maintaining a delivery pressure at the output of pump216B while recycling all the latex not delivered by pump l324 orotherwise removed. As before mentioned, the walls of the collector 216are preferably covered by a flow of latex from a distributor (616A of=FIG. 6), which provision facilitates the collection of the latexdroplets delivered by the gas stream While minimizing foaming.

As is also shown in FIG. 3, the freshly stripped latex, preferablywithout removal of its residual solvent, is delivered by pump .32A-a viaheat exchanger 325a and/or storage hold tank 324b to means for modifyingthe latex which may be used separately or in combination in thearrangement shown. The concentrating circuit 1216-1220 corresponds withthe concentrating circuit 31-32 of FIG. 1; and the modifying equipment1-224a-1233 provides for delivering the latex from pump 324g or storage324b to a polymerization reactor 1227 (either directly or afterconcentration in the concentration equipment sections 1216-1220depending on the setting of the valves 1228 and 1229), where it iscombined with polymerization catalyst, monomer, cross-linking agent,compounding ingredients and/or emulsi'iier, from selected ones ofsources :1224er to 1224 for modifying the size and nature of the latexpolymer as described more particularly in my aforesaid copendingapplications.

The modified latex from the reactor 1227 may be mixed with furtheremulsifier in mixer 1224i and may be passed to storage 1233, with orWithout first recycling it through the concentration equipment sectionand/or the polymerization reactor. Where further stabilization isdesired emulsier may be added from 324C or 324D.

Referring again to FIG. 16, the aerosol generating equipment 1114H,1114, 1115B (the connection from 1 114H to 1114 iii FIG. 16 is brokenaway to indicate provision for insertion of a homogenizer, e.g. inaccordance with FIG. 7, between pump I1114H and generator 1114, and toindicate provision for insertion of steam and/ or emiilsiiier injectorsas 114F and 114G of FIG. 3 and 4 at the discharge end of aerosolgenerator 1114) discharges into the bowl 1115A of centrifugal bowl typecoalescerseparator 1115 from which the gaseous phase (consistingprincipally of solvent-vapor) is withdrawn at 1115G to the condenser/vacuum system` The liquid phase separated in the device 1115 isdelivered to a standpipe 1115L communicating with the vapor space in1115, for the most part by way of the scoop olftake 1115E. A pump 1115Mcontrolled by the latex level in standpipe 1115]. delivers the latex tooutlet 1115N for recycle in part if desired to the input to pump 1114Hand/or to the bowl 1115A by way of nozzle 1115K through a squeeze valve1115P set to maintain a back pressure at 1115N when connected thereto.The latex coalesced and separated in 1115 is in Contact with thesolvent-vapor phase of the aerosol and therefor contains a trace ofsolvent due to the vapor pressure equilibrium. Latex of such solventcontent is withdrawn through I1115Q and heated below itsde-stabilization temperature, in heat exchanger 2115H (preferably aplate package type heat exchanger wherein the latex and steam evolvedtherefrom pass between paired plates heated by hot water circulatedbetween the pairs). The heated latex and vapor (essentially steam withbut the trace of sol-vent) are then delivered to another evacuatedcentrifugal separator 2115 similar to 1115, and the latex delivered toits standpipe 2115L is similarly delivered to outlet 2115N for recyclevia squeeze valve 2115P for further concentration in 2115H and 2115, andfor delivery to product removal 21-15Q as by pump 2115R. The latex sodelivered is generally essentially free of solvent because of the verylow solvent vapor pressure in 2115; however 2115Q may deliver to afurther concentrated 2115-2115Q is desired.

FIG. 7 at 1313 illustrates the direct connection of the solvent polymeremulsion homogenizer 113B, 213, or 313 of FIG. 2 (preferably thevibrating blade type emulsifer 313, FIG. 2) to the aerosol generator1314 as is particularly desirable when operating with an unstableemulsion in which the solvent-polymer droplets are only temporarily ofprecursor latex particle size. As is well known to those skilled in theart the vibrating blade homogenizer or Rapisonic receives emulsion atmedium pressure from a pump 1314H and forms it into a jet which impingeson the edge of a resonantly vibrating blade 1313A and the homogenizedemulsion is delivered at a low gauge pressure through a choke valve13138. The generator =1314 with streamlined nozzle 1314A is as describedin connection with FIG. 4, but may be replaced by other suitabledevices, depending on the conditions to be met, particular forms ofwhich are illustrated in FIGS. l2 to 15. In the form of FIG. 12 theconduit 514 is shaped to pro- 'vide a venturi-like section, and thediscontinuous phase is dispersed into the continuous phase (suppliedthrough 514D) by a slotted nozzle 514A located axially of theventuri-like portion of the conduit. In FIG. 13 a similar arrangement614, 614A, 614D is provided, the nozzle having an axial non-annulardischarge at the venturi-area; and the mixer 714 of FIG. 14 is similarbut with the supply connections reversed. Finally, the mixer or aerosolgenerator of FIG. 15 is similar, the latex inlet 814A beingair-insulated at 814B from any extended contact with the steamintroduced through 814D. While fluid inlets directed tangentially may beemployed, substantially linear flow at considerable velocity ispreferred at the venturi or mixing areas, especially when the mixers ofFIGS. 4, 7, and 12-15 are employed as aerosol generators.

Modifications In the form of FIG. 3 the gaseous phase and more or lesscoalesced liquid phase of the aerosol are delivered into the separator216 constituting the zone of minimum pressure in the system, and arethere preferably impinged upon liquid latex recirculated through 216.

In modifications of the invention illustrated in FIGS. 8 through ll, anadditional step is employed in that coalescence and separation of theaerosol are aided by combining the stream of aerosol and the stream ofconcentrated latex and Water vapor evolved therefrom in a mixer andintimately commingling the same before introducing them into theseparator (zone of minimum pressure).

Referring to FIGS. 8 to 1l, in these embodiments as in those abovedescribed, there is provided a moving ow 814a of gas essentiallycomprising steam as an initial continuous phase, and a flow 813e ofaqueous emulsion of solvent polymer cement. The cement preferablyconsists essentially of a dispersion of not more than 40 parts 0f thepolymer composition 4 (FIG. l) in essentially not less than 60 parts ofwater immiscible volatile organic solvent which itself, or as anazeotrope with water, has a boiling point lower than that of water. Indetermining these ratio limits other materials present, e.g. emulsifier,are not included in the calculation. An aerosol generator 814 isprovided in which the ow of emulsion 813a is dispersed, as adiscontinuous phase, in the flow 814a in such proportions that suicientheat is supplied by the steam ow 814a to vaporize substantially all thesolvent from the liquid phase into the gaseous phase of the flow in 814,to form an aerosol therein while adding the condensate formed therein tothe discontinuous phase of the aerosol. The ow of aerosol is withdrawnfrom the generator 814, and in accordance with these modifications, issubjected, in the combination hereinafter described, to a separation ofits liquid discontinuous phase from its continuous gaseous phase to forma latex by passing it into a suitable separator 816. A ow of the latexis withdrawn from the separator 816 and this flow is mixed with the flowof aerosol withdrawn from the generator 814 in a commingling means asshown as mixer 821 of any suitable construction (c g. the form of any ofFIGS. 12 to 15 may be employed) to produce the combination in which theaerosol is subjected to separation in the separator 816, so that theadmixture of the flow withdrawn from 816 with the ow of aerosol beforeits introduction into the separator 816 may assist in the coalescenceand separation of the liquid and gaseous phases. A part of the latexseparated in the separator 816 is withdrawn as output, as by pump means822.

In practicing these modifications, further improvements may be obtainedby converting to a flow of water vapor mixed with bodies of moreconcentrated latex the withdrawn stream of latex passing from theseparator 816 to the mixer 821, as by passing it through a watervaporizer 820 which may be of the plate type described above (see 220and 1220 FIG. 3). In this modification the bodies of more concentratedlatex mixed with the aerosol in mixer 821 aid in coalescing thediscontinuous phase thereof in said mixer, and the Water vapor from 820dilutes the solvent-vapor content of the aerosol and alters the partialpressures to the advantage of the latex.

As shown in FIGS. 8, 9 and 10, the aerosol from generator 814 may besubjected to coalescing stresses as by passing it through a coalescingmeans 815, similar to those above described, prior to its introductionto the mixer 821; or the mixed flow rof latex and vapor produced by themixer 821 may be subjected to coalescing stresses as by passing itthrough a coalescing means 815A similar to those above described; orboth of these provisions may be included. For simplicity, the use ofcoalescers 815 and 815A of the plate type tortuous path segregator formabove described (215, FIG. 3) is preferred.

Especially when these modifications are carried out using an aqueousemulsion of solvent-polymer cement 81311 which is unstable and has itsdispersed phase only temporarily of precursor latex particle size, it isadvantageous to add further emulsifier 823 to the fluids being mixed in821. Such addition may be effected by adding the emulsifier at the mixer0r to at least one of the flows of fluid passing thereto, as shown.

As specific illustration of the practice of the invention as a whole bythe procedures and with the apparatus above described reference may behad to the examples set forth in said antecedent application (Patent No.3,644,263) herein incorporated by reference, which are illustrative butnot restrictive, of the invention.

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that modifications and changes may be made withoutdeparting from the essence of the invention. It is therefore to beunderstood that the exemplary embodiments are illustrative and notrestrictive of the invention, the scope of which is defined in theappended claims, and that all modifications that come within the meaningand range of equivalency of the claims are intended to be includedtherein.

What is claimed is:

1. Apparatus for removing solvent from an aqueous emulsion of a solventdispersion of high polymer cement to form a solvent free latexessentially free of coagulum, said apparatus comprising, in combination:

(a) a conduit having first and second inlets and an outlet,

(b) means for passing a ow of gas comprising steam as an initialcontinuous phase into said rst inlet,

(c) a source of aqueous emulsion of solvent cement the solvent of whichitself or as an azeotrope has a boiling point lower than that of water,in which emulsion a part of the solvent cement may be in droplets ofgreater than precursor latex particle size,

(d) means for subdividing'the solvent cement droplets in the aqueousemulsion to precursor latex particle size, said subdividing means havingan inlet and an outlet, said source being connected to the inlet f saidsubdividing means for delivering said emulsion thereto, to have itsdispersed phase substantially entirely converted to latex droplets ofprecursor latex particle size therein, and the outlet of saidsubdividing means being connected directly to said second inlet todeliver the Solvent cement aqueous emulsion of precursor latex particlesize directly to said conduit for dispersion into the ow of gas thereinto form an aerosol, and

(e) means for proportioning the flow of steam to said rst inlet to theflow of cement emulsion of precursor latex particle size to said secondinlet so as to provide suicient heat by condensation of steam in saidflow to vaporize substantially all the solvent from the liquid phaseinto the gaseous phase of said ow while adding the condensate formed tosaid liquid phase.

2. Apparatus for removing solvent from an aqueous emulsion of a solventdispersion of high polymer cement to form an essentially solvent-free,coagulum-free latex, said apparatus comprising, in combination, aconduit having a steam inlet, an emulsion inlet, and an aerosol outlet;means for delivering steam into said steam inlet; means capable ofsubdividing the cement dispersion in the aqueous emulsion to precursorlatex particle size, said subdivding means being connected to saidemulsion inlet for delivering the so subdivided emulsion to s'aid inletfor dispersion in the steam ilow in said conduit to form an aerosol oflatex therein as a discontinuous phase in a solvent-vapor ow as acontinuous phase; and means for withdrawing said phases from saidconduit.

3. Apparatus as claimed in claim 2, wherein said subdividing means is anultrasonic liquid jet generator of the liquid whistle type.

4. Apparatus as claimed in claim 2, wherein said emulsion inletterminates substantially co-axially in said conduit in spaced relationto the walls thereof.

5. Apparatus as claimed in claim 4, wherein said emulsion inletcomprises a nozzle arranged substantially coaxially in said conduit.

6. Apparatus as claimed in claim 4, in which a streamlined body isarranged to extend axially within said conduit in spaced relation to thewalls thereof, and in which said streamlined body is provided with portmeans arranged symmetrically about its outer periphery, and in whichsaid emulsion inlet is connected through said streamlined body to saidport means.

7. Apparatus as claimed in claim 2, further comprising coalescing meansfor coalescing the ne liquid droplets carried by the gas phase of theaerosol, said coalescing means having aerosol inlet means and liquidandvapor outlet means, the aerosol outlet of said conduit being connectedto the aerosol inlet means of said coalescing means; and the vaporoutlet means of said coalescing means :being connected to the means forwithdrawing said aerosol phases from said conduit.

8. Apparatus as claimed in claim 7, said coalescing means comprising atortuous path phase segregating means.

9. Apparatus as claimed in claim 7, said coalescing means comprising acentrifugal phase segregating means.

10. Apparatus as claimed in claim 7, said coalescing 24 means comprisingan axial impact phase segregating means.

11. Apparatus for removing solvent from an aqueous emulsion of a cementwhich essentially consists of a dispersion of high polymer in organicsolvent to form a latex, said apparatus comprising, in combination:

(a) an aerosol generator having lirst and second inlets and an aerosoloutlet,

(b) means for passing a ilow of gas comprising steam as an initialcontinuous phase into said first inlet,

. (c) a source of aqueous emulsion of solvent cement the solvent ofwhich itself or as an aqueous azeotrope has a boiling point lower thanthat of water, said source being connected to said second inlet todeliver the emulsion of cement to said generator for dispersion into theflow of gas therein,

(d) valve means for proportioning the ilow of steam to said first inletand the flow of cement emulsion to said second inlet to provide suicientheat by condensation of steam in said flow to vaporize substantially allthe solvent from the liquid phase into the gaseous phase of said ilowWhile adding the condensate formed to said liquid phase,

(e) a separator having an inlet for mixed gas and liquid, an outlet forgas, and a separate liquid latex outlet,

(f) a latex concentrator having an inlet connected to said separateliquid latex outlet to receive a flow of latex therefrom, and having anoutlet, and comprising means for vaporizing a part of the water contentof said latex iiow to convert it into a tlow of water vapor mixed withmore concentrated latex and for delivering the same to said concentratoroutlet,

(g) commingling means having an outlet and having inlet means and meansfor connecting its inlet means to the aerosol outlet and to saidconcentrator outlet or mixing the gas and liquid phases of said aerosoland the water vapor and latex phases of said last named tiow anddelivering the resulting mixture of gas and liquid bodies from itsoutlet,

(h) means connecting the outlet of said commingling means to the inletof said separator, and

(i) means connected to the liquid outlet of said separator forwithdrawing latex therefrom.

12. Apparatus as claimed in claim 11, wherein the means for connectingthe outlet of the aerosol generator to the inlet means of saidcommingling means comprises coalescing means for coalescing the tineliquid droplets carried by the gas phase of the aerosol, said coalescingmeans having aerosol inlet means and liquid and vapor outlet means, theoutlet of said aerosol generator Ibeing connected to the aerosol inletmeans of said eoalescing means, and the liquid and vapor outlet means ofsaid coalescing means being connected to an inlet of said comminglingmeans.

13. Apparatus as claimed in claim 11 wherein the means (h) comprisescoalescing means for coalescing the liquid bodies carried by said flowand the liquid phase from said aerosol, said coalescing means having aninlet means connected to the outlet of said commingling means, andhaving an outlet means connected to the mixed gas and liquid inlet ofsaid separator.

14. Apparatus as claimed in claim 13, wherein the means for connectingthe outlet of the aerosol generator to the inlet means of saidcommingling means comprises coalescing means for coalescing the neliquid droplets carried by the gas phase of the aerosol, said coalescingmeans having aerosol inlet means and liquid and vapor outlet means, theoutlet of said aerosol generator Ibeing connected to the aerosol inletmeans of said coalescing means, and the liquid and vapor outlet means ofsaid coalescing means being connected to an inlet of said comminglingmeans.

(References on following page) UNITED 26 Fortman 116-137 Eisenkraft239-102 Markant 55-238 X Berg et al 159-47 R Tailor 159-4 B I ACK SOFER,Primary Examiner References Cited 3,064,619 3,123,305

STPTT'ES PATENTS 3,212,235 O1e3n1czak 159-4 S 3,234,995 PalmaSOn 159-47R 3,275,063 Grindrod 252-359 5 Lindsey 261-79 Cross 159-27 A Tomlinsonet al. 23-48 White 260-33.6 10 252 359 D Twaddle et al 260-93.5

U.S. C1. X.R.

